This invention relates in general to disappearing stairways, and in particular to apparatus for insulating such stairways against unwanted heat transfer when the stairway is closed.
Disappearing stairways are widely used for residential and other applications where there is a need for a stairway extending upwardly to a seldom-used area such as an attic or the like. Typical examples of disappearing stairways are shown in U.S. Pat. Nos. 2,649,237 and 2,852,176; such stairways normally fold and retract upwardly into a frame that is secured between adjacent joists of the attic, and the folded stairway is covered by a door which normally extends substantially flush with the finished ceiling of the room in which the stairway is mounted. Disappearing stairways thus take up no floor space except when actually extended, and are also inexpensive to construct as compared with fixed stairways that are typically constructed on-site, and so disappearing stairways are generally preferred for access to attics or other seldom-used areas.
Although the typical disappearing stairway is enclosed from below by a door or cover panel when folded and not in use, there may nevertheless be a substantial amount of unwanted heat transfer through the ceiling where the disappearing stairway is located. As may be seen from the foregoing patents as well as other examples of disappearing stairway construction, the folded disappearing stairway fits between joists in a space lacking the insulation that would otherwise be present in a well-constructed building. The door or cover panel forming part of the disappearing stairway is typically a relatively thin sheet of material such as plywood or the like, affording relatively poor resistance to heat flow. Moreover, the door or cover panel may fit imperfectly within the frame of the disappearing stairway, particularly where the door may have warped somewhat due to aging. The heat loss or heat gain through a closed disappearing stairway may affect the amount of energy required to adequately heat or cool a building, and can alternatively affect the uniformity of heating or cooling due to localized temperature variations in the vicinity of the stairway. The heating/cooling control thermostat is frequently located in a hallway beneath or near the disappearing stairway, and is subject to unwanted operation by air leaking out of the attic.
The nature and construction of typical disappearing stairways makes it difficult to insulate such stairways merely by adding conventional insulation. The existing door or cover to the stairway usually has a portion of the stairway folding ladder affixed to the interior of the door, and another portion of the stairway typically lies over the first portion when folded, so that typical attic insulation such as batts or loose insulation cannot practicably be applied to the inside of the stairway door. Insulation material added to the underside of the stairway door would project downwardly from the ceiling and thus would be unsightly when the stairway was folded and would still not overcome heat transfer due to drafts through a poorly fitting closed door. Insulating expedients such as proposed above would, moreover, be difficult to apply by people lacking carpentry skills.
Other types of attic structures, such as attic fans, have ceiling openings which may leak air when not in use. Although attic fans may have a self-closing door, the doors are usually relatively thin and uninsulated.